1. Field of the Invention
The present invention relates generally to crop harvesting machines and, more particularly, is concerned with a lift mechanism on a crop harvesting machine base unit which provides an auxiliary height boost to a crop gathering attachment mounted by the lift mechanism to the base unit in pivotally moving the attachment from its lowered operating position to its raised non-operating position.
2. Description of the Prior Art
Various types of crop harvesting machines typically employ crop gathering headers or attachments for delivering crop material from a field to crop material reducing elements of the machines. For example, a forage harvester for preparing forage from stalk crops, such as corn and sorghum, normally comprises a base unit having a chopping mechanism, and a crop gathering attachment which cuts the crop from the field and conveys it to the chopping mechanism. The chopped crop is then blown into a trailing wagon in which it is transported to a storage facility.
The crop gathering attachment is typically mounted at the front of the base unit for pivotal movement vertically between a lowered operating position and a raised non-operating or transport position. Some type of lift mechanism is generally pivotally mounted on the front of the base unit which, in turn, supports the attachment. The lift mechanism commonly includes an attachment support frame pivotally mounted to the base unit and an actuator which is operable to angularly displace the support frame about its pivot relative to the base unit to move the attachment vertically between the operating and nonoperating positions. Representative of the prior art are the attachment lift mechanisms disclosed in Decoene, U.S. Pat. No. 4,236,369; and Martenas, U.S. Pat. No. 4,313,294; which patents are assigned to the assignee of the present invention.
The crop gathering attachment lift mechanisms of these patents work reasonably well and generally achieve their objectives under the range of operating conditions for which they were designed. However, a need has arisen for a lift mechanism which will pivotally raise the crop gathering attachment to a height greater than can be achieved with either of the mechanisms disclosed in the above-cited patents.